Curent Position:
As
a research assistant professor in the department of materials science
& engineering, my current role is to interface between the Evanston
and Chicago campuses of the Stupp Laboratory. Other responsibilities
include directing research facilities and coordinate funding, research and
collaborative efforts at the Institute for BioNanotechnology in Medicine
(IBNAM) at Northwestern's
Feinberg School of Medicine.
Ph.D. Research: "Nanoscale Templating and Self-Assembly
of Organic Semiconductors"
Improvements
in organic electronic materials could lead to novel device applications,
ranging from large-area, flexible displays to light weight, plastic
electronics. Progress on these applications would benefit from development
of low-cost, aqueous, solution-based fabrication techniques for organic
semiconductors. Supramolecular self-assembly enables molecules to organize
in complex structures through non-covalent interactions. The nanoscale
structure and aggregation of organic semiconductors influence
conductivity, charge mobility and luminescence.
We developed
three approaches to enhance the performance of organic semiconductors
through molecular self-assembly. The first uses a liquid crystalline (LC)
template to mediate electrochemical polymerization of
poly(3,4-ethyldioxythiophene) (PEDOT), a conducting polymer used for hole
injection in organic light emitting diodes (OLED). Monomers were
polymerized in the cylindrical, hydrophobic cores of a hexagonal,
lyotropic LC formed by a non-ionic amphiphile in water. The templated,
conducting polymer films exhibited anisotropic optical properties and
increased conductivity as a direct result of the nanoscale, self-organized
structure of the template.
Figure 1: Molecular graphics illustrating
self-organization of hexagonal liquid crystalline phase.
Figure 2: Ordered, birefringent domains of
conducting polymer grown from liquid crystal template.
Figure 3: Blue emitting organic light emitting
diode (OLED) utilizing liquid crystal templated PEDOT hole injection
layer.
Another
approach was used to control molecular order by preparing organic
semiconductors that are themselves liquid crystalline. We developed a
novel series of triblock oligo(phenylene vinylene) (OPV) amphiphiles that
form thermotropic and lyotropic LC mesophases. The self-organized, layered
structure of these mesophases influences aggregation of OPV, enhancing
fluorescence in the liquid crystalline state compared with
disordered films. These OPV-amphiphiles are the first example of a
water-soluble oligo(phenylene vinylene) that can self-organize into
aligned, well-ordered, highly fluorescent films.
Figure 4: Self-assembly of liquid crystalline
OPV-based amphiphiles.
In a third
system, a triblock, dendron rod-coil (DRC) molecule containing a
quaterthiophene segment was prepared and its self-assembly and electronic
properties investigated. In non-polar solvents, this molecule formed high
aspect ratio, supramolecular nanowires
containing stacked oligo(thiophene) segments. These self-assembled
nanowires formed conductive films that were aligned by an electric field.
Using these three systems, we demonstrate how nanoscale templating and
self-assembly can enhance the performance of thiophene- and phenylene
vinylene-based organic semiconductors.
Figure 5: Self-assembled nanowire containing
conductive oligo(thiophene) core.
Publications
Hulvat, J.
F.; Sofos, M.; Tajima, K.; Stupp, S. I. "Self-Assembly and Luminescence of
Water Soluble Oligo(p-Phenylene Vinylene) Amphiphiles"
submitted for publication.
Messmore, B.
W.; Hulvat, J. F.; Sone, E. D.; Stupp, S. I. "Synthesis and Self-Assembly
of Conjugated Supramolecular Polymers" submitted for publication.
Hulvat, J.
F.; Stupp, S. I. "Anisotropic
Properties of Conducting Polymers Prepared by Liquid Crystal
Templating" Adv. Mater. 2004, 16(7),
589-592.
Hulvat, J.
F.; Stupp, S. I. "Liquid Crystal Templating of Conducting Polymers"
Angew. Chem. Int. Ed. 2003, 42,
778-781.
Links
Living In
The Materials World
Polymers Line Up
Bringing a sense of order to
plastics
Plastic Electric: The future of conducting
polymers | 
Email
James